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diff --git a/gnu/llvm/lib/Transforms/IPO/ConstantMerge.cpp b/gnu/llvm/lib/Transforms/IPO/ConstantMerge.cpp
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-//===- ConstantMerge.cpp - Merge duplicate global constants ---------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file defines the interface to a pass that merges duplicate global
-// constants together into a single constant that is shared. This is useful
-// because some passes (ie TraceValues) insert a lot of string constants into
-// the program, regardless of whether or not an existing string is available.
-//
-// Algorithm: ConstantMerge is designed to build up a map of available constants
-// and eliminate duplicates when it is initialized.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/IPO/ConstantMerge.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DataLayout.h"
-#include "llvm/IR/DerivedTypes.h"
-#include "llvm/IR/GlobalValue.h"
-#include "llvm/IR/GlobalVariable.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/Casting.h"
-#include "llvm/Transforms/IPO.h"
-#include <algorithm>
-#include <cassert>
-#include <utility>
-
-using namespace llvm;
-
-#define DEBUG_TYPE "constmerge"
-
-STATISTIC(NumIdenticalMerged, "Number of identical global constants merged");
-
-/// Find values that are marked as llvm.used.
-static void FindUsedValues(GlobalVariable *LLVMUsed,
- SmallPtrSetImpl<const GlobalValue*> &UsedValues) {
- if (!LLVMUsed) return;
- ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
-
- for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i) {
- Value *Operand = Inits->getOperand(i)->stripPointerCastsNoFollowAliases();
- GlobalValue *GV = cast<GlobalValue>(Operand);
- UsedValues.insert(GV);
- }
-}
-
-// True if A is better than B.
-static bool IsBetterCanonical(const GlobalVariable &A,
- const GlobalVariable &B) {
- if (!A.hasLocalLinkage() && B.hasLocalLinkage())
- return true;
-
- if (A.hasLocalLinkage() && !B.hasLocalLinkage())
- return false;
-
- return A.hasGlobalUnnamedAddr();
-}
-
-static bool hasMetadataOtherThanDebugLoc(const GlobalVariable *GV) {
- SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
- GV->getAllMetadata(MDs);
- for (const auto &V : MDs)
- if (V.first != LLVMContext::MD_dbg)
- return true;
- return false;
-}
-
-static void copyDebugLocMetadata(const GlobalVariable *From,
- GlobalVariable *To) {
- SmallVector<DIGlobalVariableExpression *, 1> MDs;
- From->getDebugInfo(MDs);
- for (auto MD : MDs)
- To->addDebugInfo(MD);
-}
-
-static unsigned getAlignment(GlobalVariable *GV) {
- unsigned Align = GV->getAlignment();
- if (Align)
- return Align;
- return GV->getParent()->getDataLayout().getPreferredAlignment(GV);
-}
-
-enum class CanMerge { No, Yes };
-static CanMerge makeMergeable(GlobalVariable *Old, GlobalVariable *New) {
- if (!Old->hasGlobalUnnamedAddr() && !New->hasGlobalUnnamedAddr())
- return CanMerge::No;
- if (hasMetadataOtherThanDebugLoc(Old))
- return CanMerge::No;
- assert(!hasMetadataOtherThanDebugLoc(New));
- if (!Old->hasGlobalUnnamedAddr())
- New->setUnnamedAddr(GlobalValue::UnnamedAddr::None);
- return CanMerge::Yes;
-}
-
-static void replace(Module &M, GlobalVariable *Old, GlobalVariable *New) {
- Constant *NewConstant = New;
-
- LLVM_DEBUG(dbgs() << "Replacing global: @" << Old->getName() << " -> @"
- << New->getName() << "\n");
-
- // Bump the alignment if necessary.
- if (Old->getAlignment() || New->getAlignment())
- New->setAlignment(std::max(getAlignment(Old), getAlignment(New)));
-
- copyDebugLocMetadata(Old, New);
- Old->replaceAllUsesWith(NewConstant);
-
- // Delete the global value from the module.
- assert(Old->hasLocalLinkage() &&
- "Refusing to delete an externally visible global variable.");
- Old->eraseFromParent();
-}
-
-static bool mergeConstants(Module &M) {
- // Find all the globals that are marked "used". These cannot be merged.
- SmallPtrSet<const GlobalValue*, 8> UsedGlobals;
- FindUsedValues(M.getGlobalVariable("llvm.used"), UsedGlobals);
- FindUsedValues(M.getGlobalVariable("llvm.compiler.used"), UsedGlobals);
-
- // Map unique constants to globals.
- DenseMap<Constant *, GlobalVariable *> CMap;
-
- SmallVector<std::pair<GlobalVariable *, GlobalVariable *>, 32>
- SameContentReplacements;
-
- size_t ChangesMade = 0;
- size_t OldChangesMade = 0;
-
- // Iterate constant merging while we are still making progress. Merging two
- // constants together may allow us to merge other constants together if the
- // second level constants have initializers which point to the globals that
- // were just merged.
- while (true) {
- // Find the canonical constants others will be merged with.
- for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
- GVI != E; ) {
- GlobalVariable *GV = &*GVI++;
-
- // If this GV is dead, remove it.
- GV->removeDeadConstantUsers();
- if (GV->use_empty() && GV->hasLocalLinkage()) {
- GV->eraseFromParent();
- ++ChangesMade;
- continue;
- }
-
- // Only process constants with initializers in the default address space.
- if (!GV->isConstant() || !GV->hasDefinitiveInitializer() ||
- GV->getType()->getAddressSpace() != 0 || GV->hasSection() ||
- // Don't touch values marked with attribute(used).
- UsedGlobals.count(GV))
- continue;
-
- // This transformation is legal for weak ODR globals in the sense it
- // doesn't change semantics, but we really don't want to perform it
- // anyway; it's likely to pessimize code generation, and some tools
- // (like the Darwin linker in cases involving CFString) don't expect it.
- if (GV->isWeakForLinker())
- continue;
-
- // Don't touch globals with metadata other then !dbg.
- if (hasMetadataOtherThanDebugLoc(GV))
- continue;
-
- Constant *Init = GV->getInitializer();
-
- // Check to see if the initializer is already known.
- GlobalVariable *&Slot = CMap[Init];
-
- // If this is the first constant we find or if the old one is local,
- // replace with the current one. If the current is externally visible
- // it cannot be replace, but can be the canonical constant we merge with.
- bool FirstConstantFound = !Slot;
- if (FirstConstantFound || IsBetterCanonical(*GV, *Slot)) {
- Slot = GV;
- LLVM_DEBUG(dbgs() << "Cmap[" << *Init << "] = " << GV->getName()
- << (FirstConstantFound ? "\n" : " (updated)\n"));
- }
- }
-
- // Identify all globals that can be merged together, filling in the
- // SameContentReplacements vector. We cannot do the replacement in this pass
- // because doing so may cause initializers of other globals to be rewritten,
- // invalidating the Constant* pointers in CMap.
- for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
- GVI != E; ) {
- GlobalVariable *GV = &*GVI++;
-
- // Only process constants with initializers in the default address space.
- if (!GV->isConstant() || !GV->hasDefinitiveInitializer() ||
- GV->getType()->getAddressSpace() != 0 || GV->hasSection() ||
- // Don't touch values marked with attribute(used).
- UsedGlobals.count(GV))
- continue;
-
- // We can only replace constant with local linkage.
- if (!GV->hasLocalLinkage())
- continue;
-
- Constant *Init = GV->getInitializer();
-
- // Check to see if the initializer is already known.
- auto Found = CMap.find(Init);
- if (Found == CMap.end())
- continue;
-
- GlobalVariable *Slot = Found->second;
- if (Slot == GV)
- continue;
-
- if (makeMergeable(GV, Slot) == CanMerge::No)
- continue;
-
- // Make all uses of the duplicate constant use the canonical version.
- LLVM_DEBUG(dbgs() << "Will replace: @" << GV->getName() << " -> @"
- << Slot->getName() << "\n");
- SameContentReplacements.push_back(std::make_pair(GV, Slot));
- }
-
- // Now that we have figured out which replacements must be made, do them all
- // now. This avoid invalidating the pointers in CMap, which are unneeded
- // now.
- for (unsigned i = 0, e = SameContentReplacements.size(); i != e; ++i) {
- GlobalVariable *Old = SameContentReplacements[i].first;
- GlobalVariable *New = SameContentReplacements[i].second;
- replace(M, Old, New);
- ++ChangesMade;
- ++NumIdenticalMerged;
- }
-
- if (ChangesMade == OldChangesMade)
- break;
- OldChangesMade = ChangesMade;
-
- SameContentReplacements.clear();
- CMap.clear();
- }
-
- return ChangesMade;
-}
-
-PreservedAnalyses ConstantMergePass::run(Module &M, ModuleAnalysisManager &) {
- if (!mergeConstants(M))
- return PreservedAnalyses::all();
- return PreservedAnalyses::none();
-}
-
-namespace {
-
-struct ConstantMergeLegacyPass : public ModulePass {
- static char ID; // Pass identification, replacement for typeid
-
- ConstantMergeLegacyPass() : ModulePass(ID) {
- initializeConstantMergeLegacyPassPass(*PassRegistry::getPassRegistry());
- }
-
- // For this pass, process all of the globals in the module, eliminating
- // duplicate constants.
- bool runOnModule(Module &M) override {
- if (skipModule(M))
- return false;
- return mergeConstants(M);
- }
-};
-
-} // end anonymous namespace
-
-char ConstantMergeLegacyPass::ID = 0;
-
-INITIALIZE_PASS(ConstantMergeLegacyPass, "constmerge",
- "Merge Duplicate Global Constants", false, false)
-
-ModulePass *llvm::createConstantMergePass() {
- return new ConstantMergeLegacyPass();
-}
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.